World of Warcraft users, meanwhile, have tailed off, falling from 10.1 million at the end of March, to 9.1 million at present, reports Eurogamer.
Speaking to investors in a recent earnings call, Blizzard's Mike Morhaime said that WoW players would likely come back for the release of September's Mists of Pandaria expansion, and that many had converted to Diablo 3 during its launch period.
He also spoke about the firm's plans to improve Diablo 3's end-game rewards and introduce new ways to play.
"We've already made a number fixes and updates including the activation of the Auction House, which provides a convenient way for players to trade items with each other.
"The Diablo team has also been working on improvements to end-game rewards and having a player-versus-player mode, which we hope will enhance the value and longevity of the game," he added.
During the same conference, Activision's Eric Hirshberg revealed that Call of Duty: Elite premium subscribers topped 2.3 million and that the service had 12 million registered users.
Despite the impressive figures, however, Call of Duty DLC sales were said to be down on recent years. Hirshberg hinted that a new approach might be adopted going forward.
"One consequence is the fact that a la carte DLC sales have not performed as well as in years past," revealed Hirshberg.
"Our overarching goal is to provide all of our players with the best possible community platform.
"With that goal in mind, we're always evaluating ways to improve and optimise the service to create the best experience for our fans and the best return on our investment.
"We look forward to sharing more details on this with you in the future," he added.
It was also revealed that Skylanders: Spyro's Adventure is Activision's best-selling console title for the year, although exact figures were not disclosed.
One of Activision's next major releases will be Black Ops 2, which is set during a 21st century Cold War.
It will release on November 13 on Xbox 360, PS3 and PC.
Watch a trailer for Black Ops 2 below: